JPH0634765A - Exciting coil in magnetic maker reading and identifying device - Google Patents

Abstract

PURPOSE:To provide an uniform a.c. magnetic field area with the use of only one exciting coil. CONSTITUTION:With the use of only one exciting coil including a main coil 5a and at least two auxiliary coils 5b, the auxiliary coils 5b are arranged so as to generate a magnetic field in a direction reverse to that generated by the main coil 5a. Both coils are laid above the principal plane of a belt 4, in a direction normal to the principal plane of the belt 4 so that the magnetic field intensity of given by the auxiliary coils 5b decrease the magnetic field intensity given by the main coil 5a, and accordingly, it is possible to provide a uniform magnetic field area with the use of only one exciting coil 5 including both coils in combination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exciting coil used in a magnetic marker reading / identifying device attached to an article in order to identify the type, quantity, etc. of the article.

[0002]

2. Description of the Related Art Regarding the structure of a magnetic marker reading / identifying device for reading information such as the type and quantity of an article from a magnetic marker attached to the article, Japanese Patent Application Laid-Open No. 2-2 of the same applicant
No. 90589, Japanese Patent Application Laid-Open No. 3-41387, etc. FIG. 4 is a schematic view for explaining the configuration and operation of the magnetic marker reading and identifying apparatus. In FIG.
An article 3 to which a magnetic marker 1 having a plurality of amorphous magnetic fine wires 2 having different rectangular magnetic hysteresis characteristics or magnetic flux jump characteristics with different coercive forces is attached is stretched between two pulleys (not shown) on a belt 4. It is placed on the top and moves in the direction of the arrow as the belt 4 runs due to the rotation of the pulley. Two exciting coils 5 that generate an alternating magnetic field are installed at a predetermined position in a section where the article 3 is conveyed by the belt 4 so as to be connected to an alternating current oscillator 6, and the magnetization reversal of the magnetic marker 1 caused by the alternating magnetic field is accompanied. A detection coil unit 7 in which a plurality of detection coils that detect changes in magnetic flux as an induced electromotive voltage are connected in series.
Is connected to the measuring instrument 8 below the belt 4. The measuring instrument 8 has a function of identifying the pulse voltage train generated in the detection coil unit 7 by pattern recognition.

The magnetic marker reading / identifying device as described above is
The pulse voltage train from the detection coil unit 7 is read multiple times,
The averaging is performed in the measuring instrument 8. Detection coil section
The voltage from 7 includes noise such as disturbance noise and white noise in addition to the induced electromotive voltage generated by the magnetization reversal of the magnetic marker 1. Therefore, it is possible to discriminate between the induced electromotive voltage and noise by only one measurement. Can be difficult. Noise having no periodicity with respect to time can be subjected to arithmetic averaging to reduce the noise voltage and increase the S / N ratio. Further, the pulse voltage train generated in the detection coil unit 7 is generated twice in the 1/4 cycle and the 3/4 cycle during one cycle of the AC magnetic field. When the timing at which the AC magnetic field becomes 0 is the origin of the pulse generation time, the pulse generation times differ due to the influence of the earth's magnetism. When such a pulse voltage train is added and averaged, it becomes a pulse voltage train more than the true number of pulses,
It may cause an error in reading identification. Therefore, in this device, sampling is performed only at any one time.

[0004]

In order to reverse the magnetization of the magnetic marker 1, it is necessary to make the length direction of the amorphous magnetic wire 2 parallel to the direction of the alternating magnetic field. Therefore, when the article 3 is placed on the belt 4 at an arbitrary position, the arrangement of the two exciting coils 5 is basically based on the belt 4.
The belt 4 is sandwiched between the two exciting coils 5 as shown in FIG. 3, the belt 4 is advanced so as to pass through the center of the exciting coil 5, or the exciting coils 5 are placed in the vertical direction of the belt 4. On the street.

However, depending on the structure of the article transporting apparatus, its installation location, installation method, etc., it may not be possible to install two exciting coils 5. In particular, since it is often difficult to install the two exciting coils 5 in the vertical direction of the belt 4, the AC magnetic field is generated by using only one exciting coil 5 in order to avoid the restriction of the article conveying device. It is desirable to let

When reversing the magnetization of the amorphous magnetic thin wire 2 of the magnetic marker 1, in principle, a magnetic field exceeding the coercive force on the magnetic hysteresis curve of the material is given from the outside. Sometimes, the uniformity of the magnetic field strength applied to the entire amorphous magnetic wire 2 is a problem. If the magnetic field strength applied to the entire amorphous magnetic thin wire 2 becomes non-uniform, a phenomenon may occur in which one voltage pulse waveform originally generated in the detection coil section is separated into two pulses. The pulse voltage values of these two lines are considerably lower than the pulse voltage values of one line. Alternatively, even if only one voltage pulse is generated, a phenomenon occurs in which the voltage value is considerably lower than the voltage value obtained with a uniform AC magnetic field, and this tendency is particularly remarkable in the magnetic fine wire 2 of a material having a large coercive force. Is. The reduction of the pulse voltage affects the performance of the article identification such as the reduction of the S / N ratio in the instantaneous value and the increase of the averaging number for reliable signal extraction. Therefore, even when only one exciting coil 5 is used, uniform magnetic field strength must be obtained.

By the way, the magnetic field strength and the magnetic field distribution generated by one exciting coil 5 are obtained from the Biot-Savart law, and the magnetic field strength is attenuated in inverse proportion to the square of the distance from the position of the exciting coil 5, and When a certain surface of the magnetic field distribution is fixed, the magnetic field strength at a point that coincides with the central axis of the exciting coil 5 becomes minimal, and the magnetic field strength increases as the position of the winding forming the exciting coil 5 approaches. Therefore, in order to create a substantially uniform magnetic field strength range by using one exciting coil 5, the exciting coil 5 can be ignored to such an extent that the distance between respective positions in the obtained uniform magnetic field range can be ignored.
It is possible to form a uniform magnetic field by increasing the distance to the magnetic field uniform range.

However, in such a method, in order to obtain a desired magnetic field strength in a required area, the value of the current flowing through the exciting coil 5 must be extremely increased, and
It is almost impossible for the actual installation of the exciting coil 5.
The present invention has been made in view of the above-mentioned points, and an object thereof is to provide a single exciting coil that causes magnetization reversal in a magnetic marker, and to obtain a uniform AC magnetic field region in a narrow range near the exciting coil. The present invention is to provide an exciting coil of a magnetic marker reading and identifying apparatus according to the above.

[0009]

In order to solve the above problems, the exciting coil of the magnetic marker reading / identifying apparatus of the present invention comprises:
Only one that is composed of a combination of a main coil and at least two auxiliary coils is used, and this is installed above the belt main surface in a direction in which the central axis is perpendicular to the belt main surface. Both the main coil and the auxiliary coil have a rectangular shape, and the auxiliary coil has winding parts facing each other near the bottom of the main coil so that the central axes of both coils are parallel to each other. An auxiliary coil is arranged at a position where a directional magnetic field is generated.

[0010]

The magnetic field distribution generated by the exciting coil has a larger magnetic field strength as it approaches the winding portion from the center of the coil.
Since the exciting coil of the magnetic marker reading / identifying apparatus of the present invention is configured as described above, the auxiliary coil generates a magnetic field in the opposite direction to the main coil, and the magnetic field strength generated by the auxiliary coil is smaller than the magnetic field strength generated by the main coil. As described above, the magnetic field strength of the main coil is weakened, so that a uniform magnetic field region can be expanded by using only one exciting coil in which both the coils are combined.

[0011]

EXAMPLES The present invention will be described below based on examples. The magnetic marker reading / identifying device using the exciting coil of the present invention is basically the same as that shown in FIG. 4, and therefore its illustration and description are omitted. FIG. 1 is a schematic diagram for explaining the structure of the exciting coil of the present invention, and the portions common to FIG. 2 are represented by the same reference numerals. In FIG. 1, an exciting coil 5 of the present invention includes a rectangular main coil 5a provided above the upper surface of the belt 4 in a direction in which the central axis is perpendicular to the main surface of the belt 4, and the main coil 5a. It is composed of a combination of two rectangular auxiliary coils 5b arranged such that the central axis is parallel to the main coil 5a near the winding portion, and is provided between the main coil 5a and the auxiliary coil 5b and between the exciting coil 5 and the belt. A predetermined distance is maintained during the period 4. However, the number of auxiliary coils 5b is not limited to two, and may be increased according to the substance of the magnetic marker reading / identifying device. Here, the direction of current flowing through the exciting coil 5 is the same as that of the main coil 5a, the auxiliary coil 5b is provided at a position for generating a magnetic field in the opposite direction to the main coil 5a, and the magnetic field strength generated by the auxiliary coil 5b is It is set to be smaller than the magnetic field strength generated by the main coil 5a. This way,
In the vicinity of the center of the exciting coil 5 , the magnetic field strength of the auxiliary coil 5b works so as to weaken the magnetic field strength generated by the exciting coil 5 , so that it is possible to expand the uniform magnetic field region as a whole.

FIG. 2 shows an exciting coil constructed as described above.
5 is a magnetic field distribution diagram showing a calculation result of a magnetic field distribution formed when a current flows through only the main coil 5a of FIG. In the calculation of the magnetic field distribution, the shape of the exciting coil 5 has geometric symmetry, so the shape model handles only half the size of the exciting coil 5 , and the calculation is the same as the entire shape model. I am doing so. Lines a, b, in FIG.
Each of c shows an equipotential line, and the magnetic field intensities of a are 4.20 Oe for a, 4.00 Oe for b, and 3.80 Oe for c.

FIG. 3 is a magnetic field distribution diagram showing the calculation result of the magnetic field distribution when a current is similarly passed through the auxiliary coil 5b to make the magnetic field strength uniform. The magnetic field strengths of the equipotential lines a, b and c in FIG. 3 have the same values as in FIG. As is apparent from the comparison between FIG. 2 and FIG. 3, the exciting coil 5 of the present invention, which is a combination of the main coil 5a and the auxiliary coil 5b, has a uniform magnetic field strength in the left-right direction when only the main coil 5a is used. It is further enlarged and shows good uniformity of the magnetic field strength in the vertical direction, which demonstrates the effectiveness of installing the auxiliary coil 5b.

[0014]

The exciting coil used in an apparatus for reading and identifying articles using magnetic markers is limited by the scale and installation location of the article transporting apparatus in which this apparatus is incorporated, so that only one uniform magnetic field is provided. It is desirable that the exciting coil of the present invention, which is made in response to this, uses only one of the combination of the main coil and at least two auxiliary coils as described in the embodiment. Is placed above the main surface of the belt so that the central axis is perpendicular to the main surface of the belt, and the auxiliary coil is installed at a position that generates a magnetic field in the direction opposite to that of the main coil. Reduces the magnetic field strength generated by the main coil, so it is possible to obtain a uniform magnetic field region by using only one exciting coil that combines both coils. That.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of an exciting coil of the present invention.

[Fig. 2] Magnetic field distribution diagram obtained by calculation of magnetic field distribution generated by the main coil

FIG. 3 is a magnetic field distribution diagram obtained by calculation of a magnetic field distribution generated by the exciting coil of the present invention.

FIG. 4 is a schematic diagram for explaining the configuration and operation of a conventional magnetic marker reading / identifying device.

[Explanation of symbols]

1 Magnetic Marker 2 Amorphous Magnetic Wire 3 Article 4 Belt 5 Excitation Coil 5 Excitation Coil 5a Main Coil 5b Auxiliary Coil 6 AC Oscillator 7 Detection Coil Section 8 Measuring Instrument

Claims (4)

[Claims] 1. An article in which a plurality of magnetic fine wires or thin strips are used as magnetic markers and mounted in parallel in the longitudinal direction is placed on a belt to pass an AC magnetic field band generated from an exciting coil during traveling, and It is preferable to use one of the exciting coils of the magnetic marker reading / identifying device that extracts a pulse voltage generated by a change in magnetic flux by a detecting coil provided in an AC magnetic field band, the exciting coil including a combination of a main coil and at least two auxiliary coils. An exciting coil for a characteristic magnetic marker reading / identifying device. 2. The exciting coil according to claim 1, wherein the exciting coil is installed above the belt main surface in a direction in which the central axis is perpendicular to the belt main surface. 3. The exciting coil according to claim 1, wherein the main coil and the auxiliary coil are both rectangular, and the auxiliary coil has winding portions facing each other in the vicinity of the lower side of the main coil. An exciting coil for a magnetic marker reading / identifying device, wherein the central axes of the coils are arranged in parallel with each other. 4. An exciting coil according to claim 1, wherein the auxiliary coil is installed at a position where a magnetic field direction generated by the auxiliary coil is opposite to a magnetic field direction generated by the main coil. Excitation coil of the device.